First of all, this is not really a game but it's a hundred times more entertaining than most of the games out there - if you are in the right mood that is. The Stanley Parable is like a modern take on a Franz Kafka novel in FPS style with an over-analyzer narrator and a story with no real end.
You are Stanley, an office worker. One day you realize that all your colleagues have disappeared, you are all alone in a huge office building - you need to get out, or at least find out what happened with the others. As you move around the narration helps you here and there, pointing out things, but mostly the voice just confuses you and messes up your "game" - But that's actually the point.
The best thing in the game is the humor because it's funny in ways you don't expect it to be. Along the journey you will find great gags, clever and funny solutions for moving the story ahead and most importantly the narration - without it the game wouldn't be the same. Check it out if you are ready for something different and if you don't mind that this time the game plays with you and not the other way around.